“Sea ice covers about 7% of the Earth’s surface, or about 12% of the world’s oceans.” (Wadhams)
Sea Ice can form over rough water and calm water however the process is very different.
When formed over calm water, “sea ice to form on the surface is a skim of separate crystals which initially are in the form of tiny discs, floating flat on the surface and of diameter less than 2-3 mm. Each disc has its c-axis vertical and grows outwards laterally. At a certain point such a disc shape becomes unstable, and the growing isolated crystals take on a hexagonal, stellar form, with long fragile arms stretching out over the surface. These crystals also have their c-axis vertical. The dendritic arms are very fragile, and soon break off, leaving a mixture of discs and arm fragments. With any kind of turbulence in the water, these fragments break up further into random-shaped small crystals which form a suspension of increasing density in the surface water, an ice type called frazil or grease ice. In quiet conditions the frazil crystals soon freeze together to form a continuous thin sheet of young ice; in its early stages, when it is still transparent, it is called nilas.” (Wadhams)
When formed over rough water, “at the extreme ice edge in rough seas such as the Greenland or Bering Seas, then the high energy and turbulence in the wave field maintains the new ice as a dense suspension of frazil, rather than forming nilas. This suspension undergoes cyclic compression because of the particle orbits in the wave field, and during the compression phase the crystals can freeze together to form small coherent cakes of slush which grow larger by accretion from the frazil ice and more solid through continued freezing between the crystals. This becomes known as pancake ice because collisions between the cakes pump frazil ice suspension onto the edges of the cakes, then the water drains away to leave a raised rim of ice which gives each cake the appearance of a pancake.”
During the winter sea ice continues to increase, however some of it melts in the summer. The ice that survives the summer is called “multi-year ice.” “Some sea ice is melting and this causes the redistribution of heat and salt, which plays an important role in the climate and biogeochemical systems.” (Nihashi)
Nihashi, S., Ohshima, K. I., & Kimura, N. (2012). Creation of a Heat and Salt Flux Dataset Associated with Sea Ice Production and Melting in the Sea of Okhotsk. Journal Of Climate, 25(7), 2261-2278. doi:10.1175/JCLI-D-11-00022.1
Wadhams, Peter. "How does Arctic Sea Ice form and Decay." Arctic. N.p., 1 Jan. 2003. Web. 4 Nov. 2013. <http://www.arctic.noaa.gov/essay_wadhams.html>.
“Sea ice covers about 7% of the Earth’s surface, or about 12% of the world’s oceans.” (Wadhams)
Sea Ice can form over rough water and calm water however the process is very different.
When formed over calm water, “sea ice to form on the surface is a skim of separate crystals which initially are in the form of tiny discs, floating flat on the surface and of diameter less than 2-3 mm. Each disc has its c-axis vertical and grows outwards laterally. At a certain point such a disc shape becomes unstable, and the growing isolated crystals take on a hexagonal, stellar form, with long fragile arms stretching out over the surface. These crystals also have their c-axis vertical. The dendritic arms are very fragile, and soon break off, leaving a mixture of discs and arm fragments. With any kind of turbulence in the water, these fragments break up further into random-shaped small crystals which form a suspension of increasing density in the surface water, an ice type called frazil or grease ice. In quiet conditions the frazil crystals soon freeze together to form a continuous thin sheet of young ice; in its early stages, when it is still transparent, it is called nilas.” (Wadhams)
When formed over rough water, “at the extreme ice edge in rough seas such as the Greenland or Bering Seas, then the high energy and turbulence in the wave field maintains the new ice as a dense suspension of frazil, rather than forming nilas. This suspension undergoes cyclic compression because of the particle orbits in the wave field, and during the compression phase the crystals can freeze together to form small coherent cakes of slush which grow larger by accretion from the frazil ice and more solid through continued freezing between the crystals. This becomes known as pancake ice because collisions between the cakes pump frazil ice suspension onto the edges of the cakes, then the water drains away to leave a raised rim of ice which gives each cake the appearance of a pancake.”
During the winter sea ice continues to increase, however some of it melts in the summer. The ice that survives the summer is called “multi-year ice.”
“Some sea ice is melting and this causes the redistribution of heat and salt, which plays an important role in the climate and biogeochemical systems.” (Nihashi)
Nihashi, S., Ohshima, K. I., & Kimura, N. (2012). Creation of a Heat and Salt Flux Dataset Associated with Sea Ice Production and Melting in the Sea of Okhotsk. Journal Of Climate, 25(7), 2261-2278. doi:10.1175/JCLI-D-11-00022.1
Wadhams, Peter. "How does Arctic Sea Ice form and Decay." Arctic. N.p., 1 Jan.
2003. Web. 4 Nov. 2013. <http://www.arctic.noaa.gov/essay_wadhams.html>.
Nicole Reeves